U.S. President Barack Obama speaks during a news conference with Estonian President Toomas Hendrik Ilves at the Bank of Estonia in Tallinn, Estonia, Wednesday, Sept. 3, 2014. Obama is in Estonia for a one day visit where he will meet with Baltic State leaders before heading to the NATO Summit in Wales. (AP Photo/Charles Dharapak)

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TALLINN, Estonia (AP) — President Barack Obama said Wednesday that the United States will not be intimidated by Islamic State militants after the beheading of a second American journalist and will build a coalition to “degrade and destroy” the group.

Obama still did not give a timeline for deciding on a strategy to go after the extremist group’s operations in Syria. “It’ll take time to roll them back,” the president said at a news conference during a visit to Europe.

Obama’s comments came after he said the United States had verified the authenticity of a video released Tuesday showing the beheading of freelance reporter Steven Sotloff, two weeks after journalist James Foley was similarly killed.

Obama vowed the U.S. would not forget the “terrible crime against these two fine young men.”

“Our reach is long and justice will be served,” Obama said.

In the Sotloff video, a masked militant warns Obama that as long as U.S. airstrikes against the militant group continue, “our knife will continue to strike the necks of your people.”

Obama responded that he will continue to fight the militant threat and the “barbaric and ultimately empty vision” it represents.

“Our objective is to make sure that ISIL is not an ongoing threat to the region,” he said, using an acronym for the militant group. “And we can accomplish that. It’s going to take some time and it’s going to take some effort.”

Sotloff, a 31-year-old Miami-area native who freelanced for Time and Foreign Policy magazines, vanished a year ago in Syria and was not seen again until he appeared in the video that showed Foley’s beheading. Dressed in an orange jumpsuit against an arid Syrian landscape, Sotloff was threatened in that video with death unless the U.S. stopped airstrikes on the Islamic State.

In the video distributed Tuesday and titled “A Second Message to America,” Sotloff appears in a similar jumpsuit before he is apparently beheaded by a fighter with the Islamic State, the extremist group that has conquered wide swaths of territory across Syria and Iraq and declared itself a caliphate.

British Foreign Secretary Philip Hammond told the BBC Wednesday that the masked, British-accented jihadist appears to be the same person shown in the Foley footage.

In the video, the organization threatens to kill another hostage, this one identified as a British citizen, David Cawthorne Haines. It was not immediately clear who Haines was.

Last week, Sotloff’s mother, Shirley Sotloff, pleaded with his captors for mercy, saying in a video that her son was “an innocent journalist” and “an honorable man” who “has always tried to help the weak.”

Obama said the prayers of the American people are with the family of the “devoted and courageous journalist” who deeply loved the Islamic world and whose “life stood in stark contrast to those who murdered him so brutally.”

“Whatever these murderers think they will achieve by murdering innocents like Steven, they have already failed,” Obama said. “We will not be intimidated. Their horrific acts only unite us.”

State Department spokeswoman Jen Psaki said Tuesday that it is believed that “a few” Americans are still being held by the Islamic State. Psaki would not give any specifics, but one is a 26-year-old woman who was kidnapped while doing humanitarian aid work in Syria, according to a family representative who asked that the hostage not be identified out of fear for her safety.

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